Abstract
Patients with the antiphospholipid syndrome (APS) have autoantibodies directed against epitopes on β2 glycoprotein I (β2GPI). We describe herein the performance characteristics of standardized enzyme‐linked immunosorbent assays (ELISAs) for anti‐β2GPI of the three major immunoglobulin classes: IgG, IgA, and IgM. All three assays generated highly linear standard curves (5 points, r ≥ 0.993 for each); precision was excellent both intra‐assay and run‐to‐run, with coefficients of variation (CV) ranging from 2.3% to 6.6%. Values for IgG anti‐β2GPI correlated strongly with those obtained by an earlier method (r = 0.80, P < 0.0001). A study group consisting of 203 healthy subjects was used to generate percentile‐based reference intervals for all three classes of anti‐β2GPI. APS subjects' anti‐β2GPI were found to differ significantly (P < 0.0001 for each) for those of the control population. All three assays correlated well with β2GPI‐dependent anticardiolipin antibody (aCL) measurements; IgG: r = 0.94 (P < 0.0001), for IgA: r = 0.82 (P < 0.001) and for IgM: r = 0.84 (P < 0.0001). We suggest that these ELISAs may provide valuable standardized measurements of IgG, IgA, and IgM anti‐β2GPI. J. Clin. Lab. Ana. 12:293–297, 1998. © 1998 Wiley‐Liss, Inc.
Keywords: immunoassay, autoimmunity, autoantibodies, thrombosis, coagulation, systemic lupus erythematosus, enzyme‐linked immunosorbent assay (ELISA)
References
- 1. Hughes GVR, Harris NN, Gharavi AE: The anticardiolipin syndrome. J Rheumatol 13: 486–489, 1986. [PubMed] [Google Scholar]
- 2. Galli M, Comfurius P, Maasen C, et al.: Anticardiolipin antibodies (ACA) directed not to cardiolipin but to a plasma protein cofactor. Lancet 335: 1544–1547, 1990. [DOI] [PubMed] [Google Scholar]
- 3. McNeill HP, Simpson RJ, Chesterman CN, Krillis SA: Antiphospholipid antibodies directed against a complex antigen that includes a lipid‐binding inhibitor of coagulation β2glycoprotein I (apolipoprotein H). Proc Natl Acad Sci USA 87: 4120–4124, 1990. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 4. Viard JP, Amoura Z, Bach JF: Association of anti‐β2glycoprotein I antibodies with lupus‐type circulating anticoagulant and thrombosis in systemic lupus erythematosis. Am J Med 93: 181–186, 1992. [DOI] [PubMed] [Google Scholar]
- 5. Matsuura E, Igarishi Y, Yasuda T, Triplett DA, Koike T: Anticardiolipin antibodies recognize β2glycoprotein I structure altered by interacting with an oxygen modified solid‐phase surface. J Exp Med 179: 457–462, 1994. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 6. Roubey RAS, Eisenberg RA, Harper MF, Winfield JB: “Anticardiolipin” autoantibodies recognize β2glycoprotein I in the absence of phospholipid. Importance of ag density and bivalent binding. J Immunol 154: 954–960, 1995. [PubMed] [Google Scholar]
- 7. Cabral AR, Cabiedes J, Alarcon‐Segovia D: Antibodies to phospholipidfree β2glycoprotein I in patients with primary antiphospholipid syndrome. J Rheumatol 22: 1894–1898, 1995. [PubMed] [Google Scholar]
- 8. El‐Kadi HS, Keil LB, DeBari VA: Analytical and clinical relationships between human IgG autoantibodies to β2glycoprotein I and anticardiolipin antibodies. J Rheumatol 22: 2233–2237, 1995. [PubMed] [Google Scholar]
- 9. Arvieux J, Roussel B, Jacob MC, Colomb MG: Measurement of antiphospholipid antibodies by ELISA using β2glycoprotein I as an antigen. J Immunol Methods 143: 223–229, 1991. [DOI] [PubMed] [Google Scholar]
- 10. Keil LB, Galazka M, El‐Kadi HS, Erickson Jr.EN, De Bari VA: Binding of β2glycoprotein I to activated polystyrene and its recognition by human IgG autoantibodies. Biotechnol Appl Biochem 22: 305–313, 1995. [PubMed] [Google Scholar]
- 11. Erickson EN Jr, Najmey SS, Keil LB, El‐Kadi HS, DeBari VA: Reference calibrators for IgG antibodies to β2 glycoprotein I: Preparation, properties, and availabililty to investigators. Clin Chem 42: 1116–1117, 1996. [PubMed] [Google Scholar]
- 12. Najmey SS, Erickson EN Jr, Keil LB, De Bari VA: Antibodies to β2 glycoprotein I: Standardized immunoassay and a reference interval for healthy controls. Proc Assoc Amer Physicians 108: 467–472, 1996. [PubMed] [Google Scholar]
- 13. Galazka M, Keil LB, Petersheim M, Kohles J, DeBari VA: Phospholipid‐independent binding of β2glycoprotein I by IgA from patients with antiphospholipid syndrome. Ann Clin Lab Sci 28: 153–154, 1998. [PubMed] [Google Scholar]
- 14. Dallal GE, Wilkinson L: An analytic approximation to the distribtion of Lilliefors' test statistic for normality. Amer Statistician 40: 294–296, 1986. [Google Scholar]
- 15. Hunt JE, Krillis SA: The fifth domain of β2glycoprotein I contains a phospholipid binding‐site (cys 281‐cys 288) and a region recognized by anticardiolipin antibodies. J Immunol 152: 653–659, 1994. [PubMed] [Google Scholar]
- 16. Pengo V, Biasolo A, Fior MG: Autoimmune antiphospholipid antibodies are directed against a cryptic epitope expressed when β2glycoprotein I is bound to a suitable surface. Thromb Haemost 73: 29–34, 1995. [PubMed] [Google Scholar]
- 17. Sheng Y, Sali A, Herzog H, Lahnstein J, Krillis SA: Site‐directed mutagenesis of recombinant human β2glycoprotein I identifies a cluster of lysine residues that are critical for phospoholipid binding and anticardiolipin antibody activity. J Immunol 157: 3744–3751, 1996. [PubMed] [Google Scholar]
- 18. Permpikul P, Rao LVM, Rapoport SI: Functional and binding studies of the roles of prothrombin and β2glycoprotein I in the expression of lupus anticoagulant activity. Blood 83: 2878–2892, 1994. [PubMed] [Google Scholar]
- 19. Cabiedes J, Cabral AR, Alarcon‐Segovia D: Clinical manifestations of the antiphospholipid syndrome in patients with systemic lupus erythematous associate more strongly with β2glycoprotein I than with antiphospholipid antibodies. J Rheumatol 22: 1899–1906, 1995. [PubMed] [Google Scholar]
- 20. Najmey SS, Keil LB, Adib DYR, DeBari VA: The association of antibodies to β2glycoprotein I with the antiphospholipid syndrome: A metaanalysis. Ann Clin Lab Sci 27: 41–46, 1997. [PubMed] [Google Scholar]